Technetium-99 m (.sup.99m Tc) labeled red blood cells have been widely employed in humans in applications such as nuclear cardiology, blood pool imaging, red cell mass determination, spleen imaging, accessory spleen localization, detection of gastrointestinal bleeding and hemangiomas.
A procedure for labeling red blood cells is described in U.S. Pat. No. 3,988,429, entitled "Kit for the Rapid Preparation of Tc.sup.99m Red Blood Cells", issued Oct. 26, 1976 to Powell Richards, et al. This procedure comprises the steps of supplying a sample of blood to a previously prepared, partially evacuated container containing a dry mixture of an anticoagulant and a reagent for supplying stannous ion, dissolving the dry mixture in the blood, and adding a sterile saline solution. The resulting solution containing suspended red blood cells is centrifuged to form a layer of packed red blood cells, some of which are collected. The collected cells are then mixed with a previously prepared saline solution of .sup.99m Tc sodium pertechnetate to effect the labeling.
The procedure disclosed in the above identified patent has been widely used for a number of years. However, it is somewhat cumbersome and requires considerable handling of the reagents. In addition, it has the significant disadvantage of requiring separation of the red blood cells from the plasma.
The instant invention overcomes the disadvantages of the prior art by providing a method of labeling red blood cells with .sup.99m Tc which (1) eliminates the need for separating plasma; (2) requires no centrifugation and greatly reduces handling of the cells; (3) may be conducted in one vessel without transfers, thus facilitating the maintenance of aseptic conditions; (4) tolerates greater quantities of .sup.99 Tc contamination in .sup.99m Tc eluates from the generator; and (5) is more convenient to carry out in practice.